The proposed research is designed to add additional information on the fine structure of the substantia gelatinosa. The methods to be employed are morphometric analysis, counts and classification of cells, numbers and types of synaptic terminal and number and types of synaptic contacts. These methods will be used on normal material and on spinal cord segments acutely and chronically deprived neuronal input from dorsal root ganglia and from ascending and descending intraspinal fibers. Tritiated leucine will be injected into dorsal root ganglia and spinal grey matter to identify sources of synaptic terminals.